OGC API Features - Part 5 : implement /collections/{collid}/schema and /collections/{collid}/sortables API calls - #7443

@rouault - amazing work, and great to get this in to MapServer. I've been testing out the 3 PRs altogether, and will add all comments to this PR.

(for my reference) - to build:

# Start from PR #7436
git fetch origin pull/7436/head:pr-7436
git checkout pr-7436

# add #7440
git fetch origin pull/7440/head:pr-7440
git merge pr-7440

# add #7443
git fetch origin pull/7443/head:pr-7443
git merge pr-7443

Initial notes from testing below:

Schemas (schema?f=json):

For geometry fields, we can customise the field name and format:

LAYER
  METADATA
            "oga_geometry_format" "geometry-linestring"
            "oga_geometry_name" "mygeom"
..

    "mygeom": {
      "description": "The geometry of the collection.",
      "format": "geometry-linestring",
      "title": "mygeom",
      "x-ogc-role": "primary-geometry"
    },

• Would it be appropriate to try and map a MapServer LAYER TYPE automatically rather than rely solely on oga_geometry_format? Or fallback to gml_geom_type?
• We already lookup the msOWSLookupMetadata(&(layer->metadata), "AGFO", "featureid"); - should this field be given an additional "x-ogc-role": "id" property?

CQL2

When testing querying for this Boolean field:

    "isAbandoned": {
      "description": "Queryable item 'isAbandoned'",
      "type": "boolean"
    },

• items?isAbandoned=true works
• items?filter=isAbandoned=1 - works-
• items?filter=isAbandoned=true - fails

{"code":"InvalidParameterValue","description":"Cannot parse filter: CQL2Text Expression Parsing Error: syntax error, unexpected true. Occurred around :\nisAbandoned=true\n            ^"}

Other

The following bootstrap templates are required (I can look at adding these in a follow-up PR):

• collection-queryables.html
• collection-schema.html
• collection-sortables.html

Several of the conformance links return 404s - I presume beause parts 5 and 8 are still in draft. E.g http://www.opengis.net/spec/ogcapi-features-5/1.0/conf/queryables

• Would it be appropriate to try and map a MapServer LAYER TYPE automatically rather than rely solely on oga_geometry_format? Or fallback to gml_geom_type?

done in e14a55a

should this field be given an additional "x-ogc-role": "id" property?

done in 31405ea

items?filter=isAbandoned=true - fails

fixed in f3f7a79

The following bootstrap templates are required (I can look at adding these in a follow-up PR):

added in 5166f66